Seasoning: A solid vegetable oil is recommended for the initial seasoning. Spread a thin coating of solid vegetable shortening over the entire surface, including all corners, with a paper towel. Do not use salted fats such as butter or margarine. Proceed as follows:
Gas barbecues: Preheat barbecue for 15 minutes; Turn burners to high with lid closed. Allow barbecue to heat grates for 1 to 1 1/2 hours. Turn all burners to OFF, and leave cooking grates in barbecue until they are cool.
Your cast iron cooking grates are now ready to use. To prevent rusting, they should be re-seasoned frequently, particularly when new. If rust occurs, clean with a steel brush. Reapply vegetable shortening and heat as indicated above.
Maintenance (every time you grill): Don't do a burn-off after you grill, but rather leave the cooking residues on the grates to keep a protective coating on the iron. Then do a burn-off just before you grill. Brush off charred residues with a steel brush rather than a brass brush.